Environmental campaigners have come under fire from the Liberal Democrats for failing to make enough protests in the run up to the general election.
Roads are key area for concern, say the Lib Dems
"Green groups have become too muted and the government has got away with more than it should have got away with," Lib Dem spokesman Norman Baker said.
Campaigners had become too close to ministers, he added.
Labour's Elliott Morley said the lack of protests meant the government was getting its environment policy right.
When Labour came to power green groups "had a lot of determination to try to change things", Mr Baker told environment and rural protection campaigners in Westminster.
"But they decided they could make a lot of progress behind the scenes, working with ministers."
As a result, he added, they had become "co-opted" and "part of the system".
Mr Baker, who chairs the influential cross-party environment group, refused to single out specific groups for criticism.
Mr Baker says campaigners have been "co-opted"
But speaking after the meeting to the BBC News Website, he said the movement as a whole had got "too comfortable with government".
And that was one of the reasons why the environment had slipped down the political agenda, with a general election approaching.
Mr Baker said he realised there had to be a balance between wielding influence behind the scenes and staging public demonstrations. But he added: "I just think it is a bit wrong at the present time."
He singled out "road transport" and aviation, with runway expansion and the growth of cheap air travel, as environmental problems that were "out of control".
He also said the media were to blame for ignoring climate change, although he said green groups also had a role to play in keeping that issue in the public eye.
Labour environment minister Elliott Morley said the lack of protests from green groups was a "sign of success" for the government.
Lib Dem 'hypocrisy'
But he said he did not find in his dealings with environmental groups that they had been "sub-vented" by the government.
Tim Yeo, Conservative environment spokesman, said he hoped green organisations would continue to play an important role in influencing government policy - whether behind the scenes or in public protests.
But the Green Party said the Lib Dems could never have effective environmental policies because they were too close to big business.
Its principal speaker Keith Taylor said: "These comments carry the hallmark of hypocrisy associated with all Lib Dem environmental policies.
"Despite their green fig leaf, they share exactly the same commitment to a neo-liberal big business agenda as the other mainstream parties."
The Think Environment hustings was organised jointly by the Campaign for the Protection of Rural England, Friends of the Earth, the Green Alliance, Greenpeace, The National Trust, RSPB, Wildlife Trusts and WWF - UK.